Acts 2:37 Now when they heard this they were cut to the heart, and saidto Peter and the rest of the apostles, “Brethren, what shall we do?”

It seems to me that there is a difference between these two examples. The second example where the addressees are specified in a parenthetical expression between the verb of speaking εἶπόν and the direct speech (italics) is pretty standard fare. τε πρὸς τὸν Πέτρον ... encodes syntactically the addressee relationship to the verb of speech. The function of the parenthetical clause is to indicate who is being addressed.

The first example seems somewhat different. The clause that interrupts the relationship between the verb of speaking εἶπεν and direct speech (italics) tells us the size of the audience addressed but doesn't directly encode syntactically the notion that the members of this group are the addressees. The addressee relationship is inferential and the function of the parenthetical clause is to relate the size of the group.

This may be nit picking but I couldn't find a good example of this sort of thing in Thucydides. Nothing like an exhaustive search, I looked at several forms of verbs of speaking that introduced speeches, found several examples of the second pattern but nothing like the first one. What led to to Thucydides was the grammars (Smyth, Cooper) claim Thucydides used TE solitarium for parenthetical constituents. I didn't, however, limit my search to samples that included TE solitarium.

Thank you. That is a long winded speech introduction. One might say that we have two distinct intros to the direct speech (underlined) with a parenthetical description of the head movement in between. The first speech introduction tells us the horse spoke to [him] from under the yoke. The second speech introduction tells us Hera enabled the speaking or put the words (in the mouth). On the other hand, one might argue there is only one speech introduction, the first line τὸν δ᾽ ἄρ᾽ ὑπὸ ζυγόφι προσέφη πόδας αἰόλος ἵππος and everything between that and the direct speech is a parenthetical description of the scenario: Achilles' horse speaking. A third analysis might argue that everything from τὸν δ᾽ ἄρ᾽ ὑπὸ ζυγόφι προσέφη to αὐδήεντα δ᾽ ἔθηκε θεὰ λευκώλενος Ἥρη: is a single unified speech introduction.